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Vegetable Seeds for the Tropics, Bulletiil 301 - by G.J.H. Grubben

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Vegetable Seeds for the Tropics

G. J. H. Grubben

Bulletin 301 Department of Agricultural Research

Koninklijk lnstituut voor de Tropen Amsterdam, 1978

Copyright under the Berne Convention. All rights are reserved. Apart from any fair dealing for the purpose of private study, research, criticism or review, as penritted under the Copyright Act, 1956, no part of this publication may be repro&iced, stored in a retrieval system, or transmitted, in any form or by any means, ele :tron- ic, electrical, chemical, mechanical, photocopying, recording or otherwise, wi,hout the prior permission of the copyright owner. Enquiries should be addressed to the Royal Tropical Institute, Amsterdam

@ 1978 Koninklijk Instituut voor de Tropen, Amsterdam

TABLE OF CONTENTS

1. Vegetable growing and seed supply in the tropics I 7 1.1 Introduction j 7 1.2 Economic and nutritional value of vegetables / 7 1.3 Seed supply in various growing systems / 8 1.4 Problems of vegetable seed production in the tropics / 9

2. Climatic influences / 10 2.1 Climate and vegetable growing / 10 2.2 Climate and seed production 1 12 2.3 Climate and seed storage / 13

3. Seed production for home use / 19 3.1 Selecting and harvesting / 19 3.2 Separation / 19 3.3 Drying 1 20 3.4 Storage 1 20

4. Small scale co,nmerciaI seed production j 22 4.1 Agronomy j 22

Variety testing / 22 Production of breeder seed and foundation seed j 22 Production of market seed j 23

4.2 Technology / 23 Cleaning / 23 Drying / 24 Disinfection j 25 Storage j 25 Packaging / 26 Testing / 26

4.3 Distriiution / 28

5. Seed importation / 29 5.1 Principles / 29 5.2 Varieties recommended ior the tropics j 30 5.3 List of seed companies for import / 33

6. Literature I 35

7. Names of vegetables commonly cultivated in the tropics j 38

.

ACKNOWLEDGEMENTS

Thanks are due to Dr. N.G. Hogenboom of the Institute for Horticultural Plant Breeding in Wageningen and to Mr. J. ter Veen for their comments and to Miss V.M. Russell for the correction of the text.

1. VEGETABLE GROWING AND SEED qUPPLY IN THE TROPICS

I.. 1 Introdu.ction In temperate areas vegetable growing has become an extremely technical activity.

The grower can make his choice from a great diversity of cultivars’ (varieties) which are offered by numerous seed companies. All these cultivars have been bred for prevailing climatic conditions and cultivation methods and for the quality of produce as required by the customer. The price is usually high, but the commercial grower and the common home gardener are willing to purchase these guaranteed and high quality seeds, since seed costs are only a very small part of the total production costs. Good seed pay:!

In the tropics, commercial veget able growing is increasing rapidly in order to meet the demands of the urban centres. Part of the vegetable seeds are purchased from the same large seed companies which supply growers in temnerate countries. But the fact remains that these cultivars have been bred for a climate, for cultivation methods and for customers’ requirements of quality and taste which are not at all the same as in tropical countries. On the other hand, a great deal of the seeds used by commercial growers and almost all the seeds used by the home gardener in the tropics are locally produced. This is especially true for the typical tropical species. Unfortunately, these locally produced seeds are often very heterogeneous (mixtures of different types) and their germination is poor.

This bulletin is meant to give guideli?es for local seed growers, for extension workers and for vegetable growers, both commercial and non-commercial, to obtain high quality seeds. Bad seed gives an irregular stand, weak seedlings, a low yield and an inferior product. Good seed means a good start for a high yield of good quality vegetables.

1.2 Economic and nutritional value of vegetables In this bulletin the term ‘vegetables’ will be used for plants which produce an

zlueous foodstuff, rich in water, poor in calories and mostly consumed as an addition to the starchy basic food rich in calories. Starchy tubers such as sweet potato, Irish potato, cassava, yam and cocoyam, and also grain legumes (pulses) such as common dry bean, cowpea, chick pea and horse bean fall outside our definition of vegetables. Only real vegetables propagated by dry seed are treated here, excluding the fresh one-seeded chayote fruit and vegetatively propagated types like garlic, bamboo and Sauropus,

In developing countries - which are located mostly in the tropics - the average daily per capita vegetable consumption is about 100 g against 220 g in developed countries. At least three quarters of the vegeLdbles consumed in temperate, developed countries are produced by highly technical, commercial enterprises, whereas in the tropics less than half of the consumed quantity is commercialized. These statements are broad generalizations and great local variations can be observed.

1. ‘Cultivar’ is a con;iRoniy used international word which means ‘race’ or ‘cultivated variety’. a distinct group of plants of a certain cultivated species; abbreviated as cu., plural cm.

7

Vegetables are important as protective foods, providing vitamins and minerals. The most deficient vitamin in the tropics is vitamin A. This vitamin is largely present in all darkgreen leaf vegetables and also in some other species such as carrot, pumpkin and broccoli, in the form of carotene. Vitamin C, iron and calcium are also very important. The best sources of these nutrients are the cheapest ones, the green leaf vegetables. An average daily consumption of 150 g of vegetables per capita can be taken as a target, provided that one third of this quantity consists of vegetables.

1.3 Seed supply in various growing systems The following systems for vegetable growing in the tropics may be distinguished:

a. collection of wild plants from the spontaneous vegetation. At present about 1500 vegetable species, mainly in the humid tropical lowlands and shifting cultivation areas are consumed. Some hundreds of species grow in the fields and are considered as weeds, although they are protected and consumed. This is probably less than 10% oi the total production and decreasing. Propagation is by natural seed production and spreading.

b. cultzvation for home* use in the fiel.1 generhlly in mixed croppings with other food plants, or in home gardens. About 200 vegetable species are used for this purpose and yield at least 50% of tht total production. None, or very few, inputs are used and no expenses are made for seed, fertilizer, pesticides or equipment. Nearly all the seed needed is harvested by the farmer or gardener himself; a small

: part is obtained from other farmers or bought from a local dealer. ,“i.. market gardening in mono-cultivation of a vegetable crop or in mixed plantings.

Commercial gardening may be more or less intensive, ie. with a more or less high input of labour and acquisition of seed, fertilizer, pesticides and equipment. Market gardening with about 80 species covers 40% of the total vegetable production, but it is fast increasing and very important for the alimentation of urban populations. Seed of the more local, traditional vegetables usually comes from the farmer’s own production, but seed of th t: *international’ vegetables such as onion, tomato, sweet pepper, yhite cabbage, cauliflower, cucumber, watermelon, melon, lettuce, carrots, etc. ib, often bought from dealers who import it from well-known international seed?ompanies. It is not known exactly how much vegetable seed is imported, nor which part is

locally produced for commercial purposes and which part by the farmer for his own use. A rough estimate could be that about 10% is imported, 30% comes from local commercial production and. 60% is home produced. In fact, the picture is very diverse depending on the area and the type of vegetable. Many growers buy the expensive imported seed only occasionally and harvest their own seed from the first crop for 2 to 5 generations before proceeding to seed renewal.

The actual trend, buying imported or locally produced high quality seed of high yielding modem cultivars, holds the danger of ‘genetic erosion’, i.e. the loss of traditional, local cultivars, the so-called land races. These old cultivars represent a most valuable gene stock and are the basic material indispensable for future plant breeders. They ought to be collected and stocked in gene banks.

1.4 Problems of vegetable seed production in the tropics In temperate countries, the cost of the seed is small, less than one per cent of the

total investment in a vegetable crop. This may be somewhat more in the tropics,

but the commercial grower is willing to pay a good price for reliable seeds, yet in many cases they are not available. Why is this?

The reason could be found in economic underdevelopment and a lack of good management and organization. A modem seed industry is a large scale enterprise, needing a heavy investment and many skilled people such -a plant breeders, seed agronomists and seed technologists. In most developing countries, basic food crops such as cereals and tubers receive the highest priority in’research and breeding. Vegetable breeding and seed production are given less priority than the urgently needed energy foods. Moreover, the number of vegetable species is so large that the costs of research and the establishment of a seed industry are excessively high and not in balance with the relatively small costs of seed importation.

Only a few countries in the tropics and subtropics have developed an important vegetable seed industry and have introduced legislation concerning seed pr,oduction and trade; India, Taiwan, Brazil. Other countries such as Pakistan, Egypt, the Philippines, Sri Lanka, Thailand, Mexico and Kenya are building up their own seed industry and control agency. Holrever, in most countries in the tropics the grower depends on imported, good quality b.1.t genetically not well adapted seed supplied by foreign seed companies and on uncertified locally produced, often v2i-y poor quality seed of local vegetable types. In most countries there is no legislation for seed production and no control agency to protect the producer and the grower.

In this bulletin, directions will be given to extension workers, vegetable growers and seed dealers on how to obtain *he best quality irnported seeds and how to improve the quality of the locally produced seeds. It is by no means a guide for large scale commercial seed production.

2. CLIMATIC INFLUENCES .

‘.

2.1 Climate and vegetable growing Each species or cultivar (variety), has its own special ecological requirements

concerning soil, water, temperature, hght and daylength. Unlike vegetables in temperate areas, those growing in the tropics ard almost exclusively cultivated in the open. Apart from soil type and availability of water, the climate determines wheth- er or not a given species can be grown successfully.

The most important climatic factor is temperature, We often distinguish between temperate (European-type) vegetables such as lettuce, white cabbage, carrots, cauliflower and French beans, and tropical vegetables such as kangkong, bitter gourd, yardlong bean, okra and hot peppers. It would be better to call these two groups cool-season vegetables and hot-season vegetables. For instauce white cabbage is a cool-season vegetable which is extensively grown not only in the temperate zone but also in cool parts of the tropics, i.e. in mountainous areas and elsewhere during the cool season. Tomato, sweet pepper and eggplant, on the other hand, are warm- season vegetables, well-known in the tropics but also widely grqwn in temperate areas, either the whole year round in glasshouses, or only du&g the summer months in the open. Some species have a very wide temperature range: Chinese cabbage, sweet corn, cucumber, radish, spinach beet and bunching onion are grown in areas with diurnal temperatures varying from 15 to 35’C. Other species have a narrower temperature range. Spinach, for instance, requires a diurnal temperature between 10 and 20°C, while amaranth, its tropical counterpart, performs best at temperatures above 3O’C. Table 1 gives an indication of the most suitable vegetable species for different climates,

Daylength influences flowering of plants, As far as vegetable production is con- cerned, it is important for those types which are cultivated for the fruits: solanaceous species, cucurbits, leguminous vegetables, CaulifZower, broccoli, okra, roselle and sweet corn (see Table 2). For a successful cultivation of these vegetable species in the tropics, the daylength reaction ought to be either short-day or neutral. It is an Bdvantage for leaf vegetables growing in the tropics if they react not too strongly to short days. Early flowering may decrease the total yield of leaves, it lowers the quality of the produce because it is mixed with inflorescences and hampers the harvest.

Onion cultivars grown in temperate areas during the summer months require a long day for bulbing, but cultivars used in the tropics do bulb in short days. Onions have been noted as day neutral in.Table 2, since the seed production of the bulbed onion is mainly enhanced by a cold period, regardless of the daylength. It must be noted that some vegetable species have evolved into cultivar groups with different daylength reactions. For example, okra and yardlong bean exist as short-day, day neutral and long-day cultivars. Daylength has serious consequences for seed produc- tiqn, as will be shown in the next paragraph.

Air humidity can be very high in the hot, humid tropics (> 80%) even during the dry season. iMost tropical leaf vegetables and some other species such as chayote, wing bean and yardlong bean seem to perform better at a high relative humidity.

Table 1. Climatic areas of the main vegetable types propagated by seed for cultivation in the open; mean day temperatures suitahie for (possibly irrigated) cultivation (++), possible (+), difficult (-), not suitable (--).

‘common name

tropics sub tropics temperate - --- -- !&J humid savanna mountain summer winter summer

tropics hot cool areas season season

2%35'C 30-40°C ZO-3O'C 15.30°C 25.40°C 15.25°C 15.25°C

1. Solanaccor~ vegetables sweet pepper hot peTper tomato eggplant 2. Cucurbits wax gourd watermelon melon cucumber pumpkin, squash bottle gourd loofah bitter gourd snake gourd 3. Leguminous vegetables pigeon pea sword bean hyacinth bean soybean yam bean lima bean mung bean common bean

pea wing bean broad bean yardlong bean, asparagus

bean, climbing cowpea voandzou 4. cruciFcrs Chinese cabbage (pakchoi) Chinese cabbage (petsai) African cabbage turnip mustard borecole, kale cauliflower broccoli white cabbage radish

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common name

5. Tropical leaf vegetables amaranth baseila jew’s mallow kangkong nightshade Unum New Zealand spinach 6. Various hot-season vegetables okra roselle sweet corn 7. Various cooLs;ason vegetables onion Japanese bunching o.tion leek celery asparagus qxnach beet garden beet endive

--

tropics subtropics temperate

low humid savanna mountain summer winter summer tropics hot cool areas

SCaSOZl season 28-35°C 30.40°C 20.30°C 1530°C 25-40°C 15-25°C 1525°C ,, /’

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carrot lettuce spinach

However, a high air humidity is a h -i lcap for most vegetable species, h&cause it

favours the deveiopment of pests ally obtained with irrigated ve x4

‘Id dise+es. Therefare, the best resuj& are gener- tables fn arid regions (R.H. < 60%). ,/“’

Other climatic factors @&fall, wind, radiation), although important in relation to cultivation practices, will not be discussed here.

I”

,,.’ 2.2 Climate and seed production “.”

i’ The same c!&atic factors which influence the growi& of vegetables also act on

seed production, often very pronounced. Since it i@&portant to produce disease- free seeds, it is advisable to select a dry climate oy $t least a season with a low air humidity. A dry atmosphere is unfavourable for pests and diseases and dry air facilitates the drying of the seeds. Naturally, in a humid tropical climate many vegetable seeds can be easily produced, notably all the vegetable species with a good performance (+-I-) mentioned in Table 1. However, when humidity is high special arrangements have to be made for the artificial drying and storage of the seeds. During the cultivation period, more attention has to be given to the control of pests and diseases. Both factors wiil make the production of good quality seeds more costly. See also section 4.1, the production of market seed.

.

,’ ’ . .

The daylength reaction is very important for seed production. Long-day plants do not normally flower in the lowland tropics. It has been proven that low temperatures replace the requirements for a long day to a certain extent, so that these vegetable species (many crucifers and cool-season vegetables, see Table 2) bolt and set seed when cultivated in mountain areas, above about 800 m.

Some vegetable species, more exactly the biennial cool-season vegetables, require a cold period, ranging from a few days to several weeks below 5 to 10°C, for bolting. This is true for white cabbage,‘onion (certain cultivars), leek, celery, beet, parsley and carrots. The cheap seed-to-seed method of certifie!+ seed production with the winter as natural cold period is not possible for these vegetables in the tropics, even at altitudes between 800 and 1200 m. They have to be uprooted for vernalization, i.e. putting the plants, bulbs, tubers or roots in a cold store in order to activate them to flower. The required cold period must be found experimentally for each crop and tiea. In Cuba for instance, well-developed carrot roots were stored for 60 days at 5’C before planting them out in low land during the cool season; seed yield and quality were reasonabiy good. The carrot crop produced from this seed had a quality similar to carrots produced from imported seed of the same cultivar. The question is if it is worth the costs. The relationship between low temperature and daylength reaction is not very clear. Seed setting of plants artificially made generative or cultivated at a high altitude, above 1200 m, is often very poor.

In the tropics some effort has been made to select cultivars of species normally requiring iong days a;rd/or a cold period, which will produce seed more easily in short days and at higher temperature: cabbage, cauliflower, onion. This type of breeding work is very costly, it may therefore be cheaper to move seed production to a geographic area with more favourable conditions. Yet it is important to carry out the real breeding and selection work in the vegetable growing areas, under the same circumstances as the future grower, even if seed propagation is done elsewhere.

Other factors which stimulate the initiation and further development of the generative phase, such as the C/N ratio, water stress and treatment with growth regulators (gibberellic acid) will not be discussed here, since they are only of inter- est to seed specialists.

.

2.3 Climate and seed storage Seed gradually loses its viability’ with age. This is caused by continuous enzym-

atic and metabolic activity and by respiration, consuming its reserves. Seed respiration is an important aspect of metabolic activity. This process of senescmce or ageing is accelerated by a high temperature and humidity even if the moisture content of the seed is far below that required for germination. Properly dried and caol-stored seed can retain a high viability over several years since ageing under these conditions advances very slowly. The main requirement for seed storage in a hot humid climate is to prevent the well-dried seed from regaining moisture from the atmosphere.

Seed is a hygroscopic material which is in equilibrium with the surrounding air.

1. High viability of u seed lot is its faculty, when brought in good condition forgermination.: 1. to germinate fast, 2. to show a high germination percentage and 3. to give rise to healthy seedlings.

13

Table 2. Provisional data on seed production of vegetables in the tropics: (1) fertilirction mainly by self-pollination, cross-pollination, or mixed; (2) main pollen agent for cross-pollination; (3) daylength reaction (photoperiodism) neutral = n, long day > 13h = 1 or short day < 13h = sh; (4) weight of 1000 seeds approximately, in grams: (5) seed needed for one ha of seed growing; (6) average period in months between sowing and harvesting; (7) seed yield under suitable climatic conditions; * require a cold period for bolting.

vegetable type 1 2 3 4 5 6 7

fertili- pollen day- ,p we+@ seed duration seed yield kg/ha ration agent length 1000 seeds kg/ha months normal high

1. Solanaceous vegetables sweet pepper mixed hot pepper mixed tomato self Africa,1 eggplant mixed eggplant mixed

2. Cucurbits wax gourd watermelon melon cucumber pumpkin (squash) bottle got-d loofah bitter gourd

crosb cross cross cross cross cross CTOSS

cross

3. Leguminous vegetables pigeon pea mixed sword bean mixed hyacinth bean self soybean self lima bean self mung bean self common bean self pea self wing bean self yardlong bean self cowpea self voandzou mixed

4. Crucifers Chinese cabbage (pakchoi) cross

Chinese cabbage (petsai) cross African cabbage cross tLUllip cross mustard cross kale, borecole cross cauliflowei mixed broccoli cross white cabbage cross radish cross

14

insects insects I__ insects insects

insects insects insects insects insects insects insects insects

insects insects -- -

- -

- - insects

insects insects insects insects insects insects insects insects insects insects

n n n sh shin

shin sh sh/n/l sh sh/n sh/n n n sh sh sh/n sh

n/l 1

4 1

41 n/l n sh/n n 1

5.5 3.3 3.3 3.3 4.0

70 70 25 25

170(70) 150 90 60

125 4000

330 670 400-800

30 299 170 r.00 270 220 670

.4

.5

.4

.6

.8

15 60 40 50 50

5 100 120 20 20 20 80

.6

.6 1.0 1.5 1.0 1.0

.3

.3

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4 9 5

10 7

9 9 9 4 9 4 4 3 7 6 5 4

5 6* 5 9* 6 9* 6* 6* 9* 6

60 200

80 120 200

250 250 300 300 500 400 250 250

1200 1300 900

1300 1000 500 800

1500 1100 500 700 600

509 500 600 600 600 600 150 500 600 800

100 600 150 150 300

400 400 600 800 800 600 400 400

3500 2500 2000 3000 2500 1200 2000 2500 2500 1500 2500 2000

800 800 900

1200 900 900 300 800

1200 1200

vegetable type 1 2 3 4 5 6 7

fertili- pollen day- g weight seed tation

duration seed yield kg/ha agent length 1000 seeds kg/ha months normal high

5. Tropical leaf vegetables arnarantb basella celosia jew’s mallow kangkong nightshade talinum New Zealand spinach

6. Hot-season types

okra roselle sweet corn

7. Cool-season types onion Japanese bunching onion leek celery asparaeus beet endive GuTot lettuce spinach

mixed wind shin .3 1 4 500 self sh 40 10 6 1200 cross insects sh 1 1 5 400 self sh 2 1 5 300 self? sh? 40 5 5 500? self n 2 1 6 loo? cross? insects? sh .3 1 6 200 self shin? 65 10 6 400

mixed insects sh/n 50 6 6 400 1000 self sh 30 6 6 200 400 cross wind n 150 15 4 1000 2000

c-ross cross cross cross cross cross self cross self cross

insects n insects 1 insects 1 insects 1 insects n wind 1

.

insects f 1

wind 1

1501, 2000

700 400

300 800

3.0 4 9* 400 800 2.9 4 9* 300 600 2.5 3 12* 200 600

.3 .3 9* 300 500 40 4 3 years 400 1000 16 10 9* 800 1200

1 1 9 200 300 1.2 1 9 300 1000

.8 .3 6 125 200 10 20 6 600 1200

Dry seed in a humid atmosphere takes up water from the air whereas wet seed in a dry atmosphere loses water, until after some weeks equilibrium has been reached. This equilibrium .depends on seed type and also fluctuates with temperature and with foregoing treatment, drying and storage, so deviations of 1 to 1.5% in seed moisture content may occur. See Fig. 1 for some approximate values. An increase in RH means a gradual decline in vigour because enzymatic and metabolic activity is stimulated. Above 65% relative humidity (RH) the decline is accelerated by storage fungi which are almost always present and which develop in and on the seed. A relative air humidity of 65% is considered as a safe lower limit for storage fungi and other organisms. The fungus AspergiIlus which normally develops on seed in a humid atmosphere can do no harm when the air is drier than 65% RH. Normal starchy (non-oily) vegetable seed is in equilibrium with an atmosphere of 65% RH when its moisture content ir about 12%. Fatty oil seeds of vegetables such as crucifers, cucurbits, carrot and lettuce attain this equilibrium at 8-10%. Since it is easier to measure the relative humidity of the ambient air in a storage room or of the seed-surrounding air in any container (see seed storage and testing, section 4.2). relative humidity (RH) is often used in stead of seed moisture content to indicate the effect of moisture on seed viability. Insects and mites are also favoured by a high RH. The lower limit for insect development is 30-40% RH but since disinfec-

15 L

18

16

14

12

10

8

6

4

2

% seed moisture content

corn pea bean

beet s inach

R 0 ra onion tomato pepper carrot watermelon cucumber lettuce cabbage

20 40 60 8-O ,

100

% relative humidity (RH)

Figure 1. Relation between seed molture content (wet weight base) and relative humidity in equilibrium at 25’C.

tion with insecticides is relatively easy in vegetable seed which is less bulky than agricultural seed, insects are !ess troublesome than -Flmgi,

Temperature is also an impormnt climatic factor for seed storage. Micro-organisms (fungi, bacteria) and also insects and mites are favoured by higher temperatures (25 - 35’C). The lower,limit for insects is about 5’C and for fungi 10°C. The gradual increase in deterioration with higher temperatures is probably caused by accelerated enzymatic and metabolic activity, so the cooler the seed is stored the better.

It is obvious that these two additive or interacting climatic factors, temperature and humidity, are of crucial importance for the viability of vegetable seeds. Great differences exist in susceptibility of various seed types to deterioration. Onion and lettuce seed quickly deteriorates at high temperatures and humidity. Most legumes, cucurbits, cnrcifers and also pepper and eggplant are more tolerant. Okra, pea and especially tomato seed is very robust but, naturally, the storage room must meet the minimum requirements for the weakest, short-lived seed. Harrington (1972) gives two practical rules of thumb for seed storage between 15 and 70% RH and between 0 and 30°C: 1. for each 1% decrease in seed moisture (about 10% decrease in RH) seed life is

doubled, 2. for each 5’C decrease in temperature seed life is doubled.

16

%germination lOO(

I I I 1 AH’C

RH %- 6’0”

20 25 -i-

. 0 6 12 24 36 48

months of storage

Figure 2. Schematic diagram illustrating the influence of storage temperature and relative humidity on the germination capacity of vegetable seed.

OC r- .

40

30 1 20

10

0 .

I 1 L

100 nor ton,) ‘1 short term !

/ ‘. Ciweeks to\- III

8”” ll”, v L”” ,IYIIII”

(storage fungi)

10 20 30 40 50 GO 70 80 90 %relative humidity

I 5.4 6.G 7.0 9.0 10.2 11.2 12.6 _,

%seed moisture content

Figure 3. Schematic diagram illustrating the safe storage period for vegetable seed under various conditions.

Figure 2 and 3 present simplified diagrams of the influence of temperature and humidity on the germination capacity and safe storage of a susceptible type of vegetable seed such as onion or lettuce. When it is desirable to keep the viability at a sufficiently high level for one year, an air-conditioned room with an ambient temperature of 25’C and a RH of 50% will be suitable. For longer storage, the room should be drier and/or cooler. Air-tight pack& of seed in air which is at least below 60% RH but preferably 30% further increases the longevity of the seed

I because it limits the entry of oxygen thereby reducing seed respiration.

It is believed that a certain genetic degeneration occurs by producing seed of temperate-type vegetables such as carrot, onion, lettuce and cabbage in the tropics. Although there is no evidence for this, the seed may be in a poor physical condition as a consequence of inferior growing, drying and storage conditions. Viability may be low and the seed may be infected with germs of seed-borne diseases, resulting in weak seedlings with many abnormalities. It must be judged from experience if good quality seed of a given vegetable type can be produced successfully in a certain area or if it is better to import the seed from elsewhere. In all cases, good storage conditions for locally produced as well as for imported seed is a necessity.

18

3. SEED PRODUCTION FOR HOME USE +

Almost all vegetable seed cultivated in the tropics for home consumption and a large part of the seed for commercial vegetable growing is actually produced by the farmer himself. The seed is often of a poor quality, both physically and genetically. For tomatoes, peppers, cucurbits and other fruit vegetables, growers often use the bad, diseased fruits for seed extraction. For legumes and leaf vegetables, any plant is taken, without selecting the best producers, and the seed is poorly dried and stored. Consequently, yield and quality of produce grown from this seed will not be as good as it might be if a httle more care had been given to seed production.

It is useless to prescribe technically advanced techniques for this small-scale activity, since there is not enough economic stimuius for their application. How- ever, some simple rules may be respected which guarantee a reasonably good quality seed.

3.1 Selecting and harvesting The highest yie!ding and healthiest plants with the best quality must be chosen

(selected) for seed production. The seed is extracted immediately from vegetables cultivated for ripe fruits: tomato, pepper, eggplant, cucurbits. For others, one has to wait some time in order to get well-ripe fruits or dry pods. For plants such as leaf vegetables, crucifers and onions, flowering plants and seed setting will not be achieved until after several months. In this case it is advisable to mark the best plants in the field or bed with a stick, a label, a string or twine.

3.2 Separation Three types of seed may be distinguished:

1. seeds drying on the plant Seeds of bottle gourd, loofah, all leguminous vegetables, crucifers, most leaf vegetables, onion, okra, corn, carrot, lettuce and others dry out in the pod or inflorescence on the plant. When reasonably dry, they can be collected with the pod or inflorescence and dried for some days by spreading in a thin layer on the floor or a mat in the sun, near a fire or any dry, warm. well-ventilated place. The seed is removed by hand, by rubbing or beating with a stick, the husks and the rest of the inflorescences are removed and the seed is allowed to dry mrther.

7 seed in moist fleshy fkuits -* Peppers, eggplants, melons, pumpkins and gourds should be handled as follows. If not ripe enough, the fruits should be kept in a dry place in order to ripen-off. They are then cut in halves and the seed is washed out by rubbing in ample water. The cl?a.ned wet seed is spread out on a towel or sheet of paper to dry.

3. seed in wet fleshy fruits Tomatoes and cucumbers are squeezed out into a container. The pulp is allowed to ferment for two to five days until the seed is well separated from the pulp. The seed is then washed out and dried as in 2. Good fermentation has the advantage of killing germs of diseases such as tomato bacterial canker.

19

Well-dried seed can be stored in an airtight container, for instance a glass jar with a rubber ring.

In many remote areas it is customary to store vegetable seed in a bottle gourd. This natural container is semi-airtight and protective against insect infestation when the surface is treated with oil and the neck is well plugged, but a glass jar or bottle is more satisfactory and easier to handle. Different lots can be stored together in one !arge container by packing them separately in paper or plastic bags. Opened packages of commercial seed can also be kept in this manner. If attack by insects or fungi is feared, a small amount of an insecticide (3 g of lindane, DDT, diazinon, dieldrin or malathion per kg of seed), a fungicide (thiram) or a mixture of both may

3.3 Drying Correct drying is very important if healthy, viable seed is to be obtained. When

drying is done in the sun or in a warm, ventilated place, the seed must be spread out in a thin layer, not more than a few seeds thick. When using an artificial heat source e.g. an oven or electric bulbs, and this also applies to seed dried in the full sun, care must be taken that seed temperature does not rise above 30-35’C, since a higher temperature may kill the seed. Reasonably dry seed (moisture contents lo-18%) can withstand a temperature of 35-40°C for further drying.

Small samples can easily be dried in an airtight container (e.g. a wide-mouthed jar) with a desiccant. hs a desiccant, the following hygroscopic materials may be used: . silicagel: expensive: granular: noncorrosive; can te recycled by heating; ver)

hygroscopic. . calcium chloride: chr;ip; flakes lvhich become ciammy lvhen humid; can be

recycled by heating; somewhat corrosive. . unslaked lime: very cheap, hard rock becoming dusty powder when wet; very

corrosive. . wood ash: available everywhere; must be taken very fresh but not hot; dusty

powder, slightly hygroscopic. . charcoal: like wood ash but easier to handle; slightly hygroscopic.

The desiccant should be placed at the bottom of the container, either loose or packed in a cotton bag. The desiccant is covered with a perforated metallic plate, a piece of perforated cardboard or wire mesh, and the mcist seed, packed in paper or cotton bags, is placed on top.

Silicagel k the easiest to handle. It is coloured blue with cobalt chloride which turns pink when the relative humidity rises above 45%. At that point, one quarter of its weight is absorbed water and it has to be dried before further use. About the same quantity of dry silicagel must be used as the quantity of seed, for drying from about 20% to 6% moisture within a few days. Calcium chloride, unslaked lime and wood ash are less hygroscopic so larger quantities have to be used to produce a similar effect. After two days to one week, when the seed is well dried, the desiccant should be removed.

Too severe and prolonged drying risks extracting too much water from the seed. When-it is dried to a RH below 20%, i.e. a seed moisture content of 3-5%, it might become hardcoated and as a consequence will germinate badly. This risk of induc- tion of seed dormancy is great for legumes, okra and jute maliow.

3.4 Storage

‘metically sealed

rubber ring

seed

floor (paper)

silica gel

Figure 4. Simple method for storage of small seed samples

be added. When the seeds are still too moist, a desiccant can be put at the bottom of the jar for a few days. In a very humid atmosphere, one may keep some desiccant - for instance a small package of silicagel or calcium chloride, not more than l/10 of the seed quantity - in the jar in order to keep the relative humidity low, especially after frequent opening (see Fig, 4).

jar It should be noted that it is dangerous to store a small quantity of seed in a large since the mass of humid air enclosed in the jar, especially if it is opened and

closed frequently, can be sufficient to raise the humidity of the seed above the limit for mould growth. It is better to use smaller jars% well filled with dry seed with no room for humid air or oxygen.

Normally, no desiccant is needed during storage when seed humidity and relative humidity of the surrounding air are low (< 13% and < 60%, resp.). The bulky seeds of leguminous vegetables (beans, peas) will not lose their germination capacity even when stored in an open container or in a cotton bag in a reasonably dry place (RH < 70%). These seeds are very attractive to insects, so it is necessary to disinfect with an insecticide. Care should be taken that beans or peas treated with an insecticide are not used for consumption by accident.

If carefully dried and stored, most species will retain good germination power for several years. The safest method is to renew the seed every year, or at least after two ye&s, throwing away the old stock.

Most vegetable seeds do not germinate well when used too fresh. It is better to start using the seed after a storage period of at least two weeks.

21

4. SMALL-SCALE COMMERCIAL SEED PRODUCTION

Horticultural stations and also private seed growers sometimes sell locally produced vegetable seeds to individuals. This can be seen as the first step towards a large scale national production of certified vegetable seeds. h high level and large-scale seed industry has already been built up in India, Taiwan and Brazil and is in progress in Egypt, Pakistan, the Philippines, ,LIexico, Sri Lanka, Thailand and maybe in some other countries in the tropics. These seed industries are mostly governmental but sometimes also private. They use skilled plant breeders, seed agronomists, seed technicians, and modem processing equipment. The bulk production of certified seed is confined to mechanized farms on a contract basis. Small-scale seed industries, however, have only limited resources and lack skilled seed specialists. Some technical recommendations will be given here for seed production by small-scale seed enterprises. lt may be seen as a type of intermediate seed technology between the traditional ‘primitive’ system and the technically advanced one. The organization scheme of a modem vegetable seed industry and the relation with the control agency is presented in Fig. 5. For methods to establish a small-scale seed industry, the same set of operations should be followed.

4.1 Agronomy

Variety testing First of all, a choice has to be made of those species and cultivars which can be

used for seed production. To begin with, all popular local and +ported types and cultivars should be tested. Eventually, a very small number of cultivars may be chosen which meet the requirements for both grower and consumci. As production of hybrid seed is a complicated and difficult process for a newly developing seed industry, only open-pollinated cultivars should be chosen.

Boduction of breeder seed and foundation seed Breeder seed or nucleus seed is seed from the selected cultivar, produced in a

small quantity as a basis for the production of foundation seed. The selected cultivars are planted in smali, well-isolated fields, self-pollinating species 100 m and cross-pollinating species at least 500 m apart. The proper segregation distance depends on wind direction, area of the fields, degree of cross-pollination and desired purity. A barrier crop, for instance maize, can be used to make the segregation more safe. The plantings should receive very strict selection (roguing) i.e. removal of all the off-types starting before flowering. Some superior plants are harvested separately and their seed is used for the next generation of breeder seed and also for future selection and breeding. The seed of the rest of the plants is bulked and used for the production of foundation seed.

Foundation seed, also called elite seed or stock seed, is seed resulting from a controlled propagation of breeder seed and is produced in a medium/large quantity to be used by the seed grower for the production of certified market seed. The same production methods as for breeder seed must be practised. For small-scale

22 w

seed production, breeder seed may be directly used for the establishment of fields of market seed.

Reduction of market seed Market seed is seed produced by the seed grower from foundation seed (or from

breeder seed) certified as to purity and trueness-to-type by a control agency and destined for sale to the vegetable gro&ers. This seed is called ‘certified’ here, but it must be clear that it merits this title only when an independent control institution for the certification of vegetable seeds exists. The previous steps, the production of breeder seed and foundation seed, have to be carried out in the same area and under the same conditions as those prevailing for the vegetable growers. The bulk production of market seed, however, can be done in any area which best mee:s the requirements for seed growing (see section 2.2 page 12): . a dry atmosphere favourable for a healthy crop; . no heavy rainfall during blooming, since this endangers good pollination of cross-

pollinating species; . temperatures must not be too low or too high since these cause poor fruit

setting; a diurnal temperature between 25’ and 35’C will be convenient for warm-season vegetables, and 15’C to 25’C for cool-season types; pollen and ovaries may be killed above 35’C or under 10°C, but these values vary with the species;

. dry weather during the harvest period of crops with seeds drying in the pods or I;lflorescences;

. strong winds which would cause shattering of seed on the plant should not occur.

The crcp must be sufficiently isolated. Roguing of diseased plants (especially with virus symptoms) and off-types must be carried out regularly. Pests, diseases and weeds mu:t be strictly controlled. Since the produce is not destined for consumption, frequent treatment with toxic pesticides can be carried out if necessary. ‘Cultural practices are largely identical to the system used for commercial vegetable growing. However, planting distance should be much wider. The cultivation period will last much longer, which means more chances for pests and diseases.

Harvesting and eventually threshing can be carried out, depending on ‘the extent of the production and on local circumstances, by hand in one or more rounds or, in technically more advanced areas, mechanically. Once the seed has been harvested, the agronomic part of the seed industry is terminated and seed technology or preparation for sale can start.

4.2 Technology

Cleaning For separation of the seed from the plant part:;, the same categories and tech-

niques can be used as described for home-produced seeds (section 3.2). For larger quantities, however, some technical aids can be applied; threshing by beating with a stick or mechanically and winnowing in the wind or with a fan. It is better to use a hand- or motor driven winnowing mill with trays and sieves, which removes husks, dust, seeds of weeds, deaf seeds and other impurities and which grades the seed.

Separation of the seed of fleshy fruits is done as described in section 3.2. For tomato and cucumber, a cleaner and faster method is to squeeze the fruits in a large

23

seed company activities of the

departments operations control agency

.I

. .

1. Agronomy Research unit variety testing

breeding, selection breeders seed propagation

c foundation seed

testing for release

control

Production unit

2. Technology

production fields roguing harvesting threshing

4 bulk seed

field inspection

drying cleaning pading storage dressing testing packaging

+ market seed

seed inspection

3. Distribution promotion marketing transport retail trade

Figure 5. Scheme of an advanced seed industry

control

container and to add one liter of 40% hydrochlorid acid per lO@ 1 of squeezed mass. After 30 minutes the seed can easily be washed off from the flesh. The disadvantage of this method is that it does not kill germs of diseases such as bacterial canker of tomato, and the seed coat may be slightly damaged by the acid, so most seed producers prefer the fermentation method.

Dying The seed can be dried by spreading it out in a thin layer in the open on a cement

floor or on a mat, or artificially by air which is heated and rhea blown over or through the seed with a fan. The higher the moisture content, the lower the drying temperature in order to avoid injury. For very moist seed with a moisture content of over 18%, the drying temperature must not exceed 35’C. Under 18% moisture,

24 a

the seed can safely be dried with air of 35-40°C and under 10% with air of 45OC. One must be especially careful with weak seeds such as onion and lettuce. The high ambient air temperature and relative humidity in the tropics are a great handicap. The risk of seed damage can be avoided by using air of ambient temperature which has been dried by passing through silicagel or by a combination of heating and a dehumidifier.

The seed must be dried to a moisture content of not more than 8% for oily seeds (Brassicas, cucurbits) or for very small seeds (lettuce) and not more than 12% for legumes and other large, non-oily vegetable seeds, in equilibrium with a RH of 50%. .\t 25’C this seed keeps viable for one or two years. For long-term storage, more than five years, it would be safer to dry to a point in equilibrium with a relative humidity of 3040%.

Disinfection Insects, spider mites and storage fungi have little opportunity to spoil well dried

seed, but they multiply rapidly when the moisture content is critically high, causing a quick decline of seed viability. Germs of seed-borne fungal and bacterial diseases survive on the seed coat or in the seed and attack after germination. It is a normal procedure to disinfect all commercial seed against insects and seed-borne diseases. Seed above 65% RH, disinfected with a fungicide such as pentachloronitrobenzene or an antibiotic (puromycin, chloramphenicol) can sometimes keep better tha:i non-disinfected seed, but in most cases the fungicide will not penetrate well enough into the dried seed to kill also the storage fungi. Therefore, it is necessary to dry the seed to a moisture content below 65% RH in order to prevent deterioration by fungi. It is easier to disinfect against insects. Suitable insecticides are lindane (3 g/kg), carbaryl (10 g/kg), dichlorvos and pyrethrum. Some commonly used products against microorganisms are mercury-fenyl or -methyl (2 ml/kg), thiram (3 g/kg) and benomyl (4 g/kg). These products may protect the seed to some extent against storage fungi, but their principal function is to act as a seed dressing, i.e. to protect . . the young seedling after germination. Many products are commercially available. The fungicides benomyl and thiram and the insecticides carbaryl and bromophos are often used as seed dressings. These dressings can best be given just prior to packaging. Care must be taken, for chemical prestorage disinfection and for seed dressing, that the dosage on the label of the commercial product is not exceeded, because an overdose may damage or kill the seed.

For killing storage insects in well insulated stores for large quantities of seed fumigation is often used. It is also a suitable method for cleaning the store room itself. Capsules or tablets in plastic bags may be used, for instance for storage of beans. These chemicals (methylbromide, phosphine, hydrocyanic acid) may affect the seed viability when too large dosages are used, especially when the moisture content of the seed is high. They are very toxic to man, so one has to be careful when carrying out fumigation.

Storage Small quantities of not more than a few kilogrammes of seed can easily be stored

in airtight containers, possibly with a desiccant, in a cool place or in a refrigerator. Usually this will be impractical or impossible for larger commercial stocks. Well dried and cleaned seed should be kept in good condition right up to the time of distribution and use. It is clear that in a humid tropical climate special arrangements

25 L

should be made to counteract ambient humidity and temperature. The best method is the installation of a cold store (temperature < 10°C, relative humidity < 50%). If this is too expensive, an air-conditioned room (temp. < 25’C, RH < 50%) would be a good alternative, in order to keep the seed in a good state for at least one year. If such facilities are not available, the seed should be stored as fresh, ventilated and cool as possible. The seed store room must always be kept very clean in order to avoid infection and to keep rodents out.

It has been shown that in the hot humid tropics the relative humidity of a storage room of 50 m3 can be kept below 50% with a small one h.p. air-conditioner provided the room is well insulated. It must have thick: oil-painted walls, no win- dows 2nd a well-insulated double entry door. Arrificial insulating materials such as plastified fiber board which might give off toxic gases affecting seed viability should not be used.

It is necessary to control the temperature and relative humidity of the seed storage room from day to day, so it must be equipped with a thermometer and a hygrometer. .4 simple hair hygrometer is not accurate enough, a more reliable type, for instance a wet and dry bulb hygrometer, should be used.

Pat kaging In a humid climate it is advisable to have an air-conditioned packaging room next

to the storage room. The easiest way of packing is the use of moisture-proof heat-sealed polyethylene bags of 0.25 mm thickness (at least 0.1 mm = 400 gauge) with a label indicating the origin (seed company), variety, harvest month and year, sample number, weight, treatment given and toxicity warning, seed test data and percentage of germination and, if possible, recommendations for sowing. Each variety should be packed in two or three different quantities, for instance small size packets (50 m2 planting), medium (500 m’) and large (5000 m’). Another possibil- ity is to make packets of a certain weight, for instance 2.5 and 10 g for small seeds and 100 or 200 g for legumes and other large seeds. Other packaging methods, more expensive and complicated, are used by large seed companies: aluminium laminated multi-wall paper bags with printed text, or vacuum tins. It is important that the seed should be packed in a ‘tropical’ vapourproof material.

Testing Seed delivered by the dealer to the grower must be highly reliable. Germination

tests of seed lots for trade should be carried out regularly. It is recommended to follow the instructions of .the ISTA (Anon. 1976) as much as possible. A fairly reliable picture of the seed viability can be obtained as follows. Spread four samples of 50 seeds on moist paper in petri-dishes and put them in a room ambient temperature (20-3O’C). Moist sand can be used for large seeds such as beans. The germi- nated seeds are counted and removed from the dishes every other day during lo-14 days. When less than the rninirnum prescribed percentage germinates within this period the lot should not be used for distribution.

For hard-coated seeds such as okra, New Zealand spinach, jew’s mallow, peas and beans, which have been stored under very dry conditions, scarification, previous soaking for one night or dipping in water of over 90°C for a few seconds or for larger quantities in water of 55’C during 20 minutes may be required in order to get good germination. This should also be indicated on the label. Minimum germination percentages as legally required in the USA are presented in Table 3. These

26 ”

Table 3. Minimum official germination percentages as laid down in the Federal Seed Act, USA. Completed with unofficial percentages which might be used for tropical vegrtabks (*). estimated on the basis of experience; h = including hard seed. -

1. Solanaceous vegetables African eg,T!ant eggplant pepper (sweet, hot) tomato tomato, husk

2. Cucurbits cucumber melon pumpkin squash watermelon other cucurbits

3, Leguminous vegetables common (French) bean cowpea lima bean pea yardlong bean other legumes

4. Crucifers African cabbage broccoli cauliflower Chinese cabbage kale mustard radish turnip white cabbage

50* 60 55 75 50

80 75 75 75 70 70*

70h 75h 70h 80h 75h 70*h

75* 75 75 75 75 75 75 80 75

5. Tropical leaf vegetables amaranth basella jew’s mallow kangkong nightshade talinum New Zealand spinach

6. Various hot-season species okra roselle sweet corn

7. Various cool-season species asparagus beet (spinach, garden) carrot celery endive Japanese bunching onion leek lettuce onion spinach

80* 60* 50*h 70* 60* 60* 40h

50h 50* 75

70 65 55 55 70 70 70 80 70 60

percentages may also be used by countries lacking legal rules for seed quality. For tropical vegetable species which are not mentioned in this list, the same percentage as for the most similar or most related seed type from the list may be used.

Another test commonly executed in si?d laboratories is the determination of the seed moisture content. However, determination of seed m&ture content with the air-oven method is laborious, difficult for non-professionals and requires too much precision. Measurement of the seed moisture content with an electric humidity testing apparatus is also not easy for the relatively small lots of vegetable seed. This apparatus must be adjusted separately for each seed type. The most practical method is not to control the seed moisture content but the relative humidity in the seed lot. A cheap instrument (about $ 100) is the dip-shaft hygrometer, the most accu-

27

rate and easiest type is an electronic hygrometer equipped with a piercing probe (ahout $ 1500). This apparatus is easily transportable, works also on batteries and is suitable for small quantities. It can be used for any seed type and is not affected by impurities or dirt. The equilibrium relative humidity in the seed (abbreviated as ‘30 ERH) is correlated to the seed moisture content as explained in section 2.3 and Fig. 1. It clearly indicates if the seed is well dried.

An official, independent control agency will not only test germination percentage and moisture content, but also other factors determining the quality. The seed should be viable, free from seed-borne diseases, weed seeds and other impurities. Moreover, it should be genetically pure and true to the name of the cultivar, a requirement tb.at is not easy to control since there is a great resemblance between various cultivars of a species. This ‘testing for genuineness’ protects the producer of the cultivar and also the vegetable grower from falsifications and errors. Lacking a control agency, the seed producing institution should take every precaution to ensure delivery of first class seed.

4.3 Distribution iMuch emphasis is placed on the necessity for a good distribution system. Without this, all the care given to the production of high quality seeds is wasted. In many countries it will not be easy to set up a good distribution system and to reach the vegetable growers, in spite of the apparent need for quality seed. Seed is sold in market stands, in shops for foodstuffs or other goods, in equipment and material stores, by agricultural or horticultural extension agencies and in cooperative stores. Seed may also be ordered by mail from a local dealer or from abroad.

If vegetable seed arrives at the distribution centre in good condition it may deteriorate during the weeks or months of storage and exposure to high temperature and humidity before it is sold. If the retailer has no convenient place to store the seed and the climate is a real handicap then he must make arrangements to renew his stock regularly after some weeks and to order no more than what he &I sell in that period.

In seed technology, many levels of sophistication exist between +e simple techniques for obtaining small quantities for home use and large scale commercial seed production. For information on cheap and easy-to-handly equipment and the more advanced large scale techniques, one may contact the Ministry of Agriculture in the home country or one of the following two addresses:

1. International Seed Testing Association (ETA) ISTA Secretariat Reckenholz P.O. Box 412 CH-8046 Ziirich, Switzerland

2. Seed Industry Development Programme Division of Piant Production and Protection @A0 Via delle Terme di Caracalla Rome, Italy

28

5. SEED IMPORTATION

5.1 PrincipIes When ordering seed from abroad, it is important to consider: 1. which is the best

variety, 2. how to get good quality seed of that variety and 3. for a reasonable price.

1. variety. Variety testing of foreign cultivars has been carried out in most countries. Often the grower or seed dealer knows from experience which cultivars perform well in the area. Yet it is not uncommon to see packets of seed for sale in warehouses in the lowland tropics containing seed of temporate vegetable types which can never be grown successfully in that area! Variety testing should be a continuous experiment to be repeated regularly with the appearance of new varieties. It is mostly an activity of national experimental stations.

2. quality. Seed must be delivered in tropical, vapourproof packages in order to avoid rapid deterioration. Most international seed companies deliver retail vegetable seed in vapourproof, aluminium-laminated packets which can be safely stored for several months in a humid, hot atmosphere without losing much of its germination capacity. They should be kept in a refrigerator, cold store or air-conditioned room. Dealers who import seed in bulk and re-pack them in small packets often keep the opened tins or bags in a warm humid place, causing a quick decline in viability. It might be better to import the seed in retail packages. Also, much depends on the facilities for getting seeds through customs in a short time and on quarantine and import regulations.

3. price. Good quality seed pays. Although the price of the vegetable seed is only a small part of the total costs, it is worthwhile to find out which company offers good quality seed for the best price. The price of vegetable seeds may show wide variations, as illustrated by the figures given in Table 4. In general, prices of Western European companies are somewhat higher than those of companies in the USA. South African, Taiwanese and Japanese seeds are even cheaper and Indian companies offer seed for the lowest price. Naturally, new varieties are often more expensive than older ones because of development and promotion costs. The high price of hybrid seeds is due to the high amount of labour involved in hand pollination and to a relatively low rate of seed production. A new technique in the preparation of vegetable seeds is to coat the seed with a clay-like substance, making each seed a regularly shaped globule (pelletization). This reduces the amount of seed needed considerably, facilitates mechanical sowing and decreases the risk of failure. Pelleted seed, however, is very expensive and up to now rarely used in the tropics.

A list of cultivars generally recommended for the tropics is presented on the following pages, a list of seed companies in paragraph 5.3. The easiest way of ordering

Table 4. Rices of seeds of popular non-hybrid vegetable cuftivars (Jo. b., in US 8) in medium size package (X-1 kg). Average of some European, North American, African and Asian seed companies as presented in seed catalogues of 1976.

vegetable type method price in seed needed cost of seed US8 per kg gper lOOva US8 per 100m2

- mean range

tomato transplanted 80 2 -1500 3 .24 sweet pepper transplanted 60 36 -1700 4 .24 eggplant transplanted 40 11 - 500 5 .20 cucumber direct sowing 20 13 - 240 10 .20 melon direct sowing 25 13 - 240 8 .20 French beans direct sowing 3 1.5- 8 800 2.40 pea direct sowing 3 1.5- 10 1500 4.59 cabbage transplanted 35 7 - 124 3 .lO cauliflower transplanted 60 18 - 320 4 .24 onion transplanted 50 7 - 60 50 2.50 beet direct sowing 20 4 - 240 200 4.00 GiZc\t direct sowing 15 7 - 32 80 1.20 lettuce transpianted 45 7 - 460 8 .36

vegetable seed is a permanent contact with one single company, but it may be wiser, considering the variation in prices and cultivars, to order more specifically the best and cheapest cultivars from different companies. However, when good quality seed of a given vegetable type is offered locally, it is not necessary to order it from abroad.

5.2 Varieties recommended for the tropics In the following list a number of varieties (cultivars) has been com$ed which are

commonly used for cultivation in the tropics or have been proven in variety tests to be superior to others. Many popular local varieties exist and are superior to imported ones .in yield and resistance to diseases or simply more in agreement with the local taste. If good local varieties are present, then it is better to produce good quality seed from these than to import foreign varieties.

Much depends on traditional relations with seed companies. Japanese and Chi- nese, and Australian and New Zealand companies to a lesser extent, are the most popular in South East Asia. India produces its own seed and also China is largely self-supporting. Middle Eastern, Mediterranean and African countries import a great deal from France, The Netherlands, England and Denmark. Israel and Egypt are partly self-supporting. East Africa obtains part of the required seed from a South African company. About ten North American companies deliver the greatest part of vegetable seed to Latin America. Here, only Brazil and Mexico have established an important seed industry.

The varieties named in this list are not described in detail. The reader is advised to order seed catalogues for data on characteristics of interesting varieties and to order seed samples for variety testing.

30 m

1. SOLANACEAE

eggplant: local varieties; Black Beauty, Black Magic, Florida High Bush, Florida Market, Jersey King, Long Purple, Pusa Purple Cluster

hot pepptr: local varieties; Anaheim, Caribe, Fresno, Long Red Cayenne, Red Chili sweet pepper: local varieties; Burlington, California Wonder, Florida Giant,

Keystone Resistant Giant, Ruby King, World Beater, Yolo Wonder tomato: local varieties; AVRDC 24, Best of All, Bonset, Calypso, Campbell, Flora-

del, Heinz 1370, Homestead, Indian River, Isabella, Manalucie, IManapal, iMar- globe, Moneymaker, Panase, Parker, Piacenza, Piervil, Pritchard, Roma, Rossol, Rutgers, San ,Marzano, UHN Hybrid 52, Vemone, VF 1402

2. CUCURBITS

bitter gourd: local varieties; Coimbatore Long bottle gourd: local varieties; Pusa Summer Prolific Long cucumber: local varieties; Ashley, Cherokee, Chinese Long, Fengshan Green,

Gemini, Japanese Long Green, Poinsett,‘Southem Cross loofah: local varieties; Pusa Chikni

. .

melon: local varieties; Burpee Hybrid, Dessert Sun, Dulce, Gulfstream, Hale’s Best, Honey Dew, Imperial 45, Smith’s Perfect, Supermarket

pumpkin: local varieties; Butternut, Cheese, Cushaw, Sugar snake gourd: local varieties squash: /Ambassador, Cocozelle, Crookneck, Long French Bush, Long White,

Straightneck, Zucchini watermelon: local varieties; Charleston Grey, Congo, Crimson, Dixie Queen, Fair-

fax, La Mallorca, Mississippi, Sugar Baby, Sunrise, Sweet Carnival

3. LEGUMES

Bambara groundnut: local varieties broad bean: local varieties; Long Pod common bean (snap bean, French bean):

- bush type (bush bean): Canadian Wonder, Contender; Fin de Bagnols, Semi- nole, Stringless, Tendergreen, Top Crop, local varieties

- pole type (climbing bean): local varieties; Canfreezer, Florigreen, Kentucky Wonder, Witza

cowpea: local varieties; Pusa Barsati hyacinth bean: local varieties; Pusa Early Prolific, Waby Salad Bean lima bean:

- bush type: Fordhook 242, Henderson, Ventura - pole type: local varieties; Carolina, Easy Shell, Sieva

mungbean: local varieties pea: local varieties; Arkel, Bonneville, Blue Bantam, Little Marvel, Mammoth, pigeon pea: local varieties soybean: local varieties; Giant Green sword bean: local varieties winged bean: local varieties yardlong bean (asparagus bean): local varieties; Extra Long

31 L

4. CRUCIFERS

broccoli: Calabrese, Type A, Green Sprouting cabbage: Copenhagen Market, Drumhead, Gloria Osena, Goldrn ;\cre, KK-cross,

KY-cross, Tainong Hybrid All Season, Titan 90, Ursa, Yehsen, local varieties cauliflower: local varieties; Early Market, Early Patna, Pua Kea, Snowball, Snow

Diana, Snow Peak, Snow Queen Chinese cabbage:

- pakchoi (leaf type): local varieties; Taisai - petsai (heading type): local varieties; Cantonner Whitehead, Granat, Kyoto, IMichihli, Nagaoka, Tropicana, Waka, Wongbok

leaf cabbage: - African cabbage: local varieties - kale (borecole): local varieties; Thousand Headed kale - mustard: local varieties; Prize Winner

radish: - European: French Breakfast, Globemaster, Scarlet Globe - Chinese: lo&l varieties; Japanese White

turnip: White Globe

5. TROPICAL LEAF VEGETABLES

amaranth: local varieties; Bari chaulai, Katwa Data, Tampala basella: local varieties; Malabar Spinach jute: local varieties kangkong: local varieties nightshade: local varieties talinum: local varieties New Zealand spinach: New Zealand

6. VARIOUS WARM SEASON VEGETABLES

okra: local varieties; Clemson, Emerald, Ladyfinger, Louisiana, Pusa Sawani roselle: local varieties sweet corn: local varieties; Branco, Cuhana, Golden Bantam, Puerto Rico 50, Super-

sweet, IJSDA 34

7. VARIOUS COOL SEASON VEGETABLES

asparagus: Glory of Brunswick, Mary Washington carrot: Chantenay Red Core, Danvers Half Long, Imperator, New Kuroda, Pusa Kedar. local varieties celery: Golden Self Blanching, Plein Blanc Do&, Summer Pascal endive: Batavian Broad Leaved, Green Curled garden beet: Detroit Dark Red, Detroit Nero, Egyptian, Rouge Noire Plate Japanese bunching onion: local varieties; Long White Bunching leek: Gros Long d’Eti, Italian Giant, Large American Flag, Musselburgh lettuce:

- butterhead: Kagraner Summer, Prado, Reine de Mai

32

- loosehead: local varieties; Simpson - crisphead: Great Lakes, Iceberg, Reine Je Glace

onion: local varieties; Bombay White, Bombay Red, Crystal Wax, Excel, Red Creole, Texas Grano 502, Tropicana Tropic Ace, Yellow Granex

parsley: Paramount, Triomphe spinach: Saloniki, Viroflay spinach beet: Lucullus, Pusa All Green

5.3 List of seed companies for import Some addresses of seed growers with frequent deliveries to tropical and subtrop-

ical countries have been compiled. The list is purely informative and not restrictive. National seed companies not exporting are omitted.

Australia India

Yates & Co. 90-l 00 Sussex Street P.O. Box 2707 GPO Sydney

Brazil

Agroceres S.A. Avenida Dr. Vieira de

Carvalho 40-3. Andar Caixa Postal 30.723 Sao Paul0

National Seeds Corporation Beej Bhavan, Pusa Complex New Delhi 110012

Pocha’s Seeds P.O. Box 55 1A Middle Road Poona 411001

Suttons Seeds 13-D Russell Street P.O. Box 9010 Calcutta-l 6

Em@

Horticultural Research Institute

Giza

Israel

Haxera Seed Co P.O. Box 1565 Haifa

France Japan

Clause Bretigny-sur-Orge Seine-et-O&e

Tezier B.P. 223 Valence-sur-RhBne

Viimorin Andrieux 4 Quai de la Megisserie 75001 Paris

Fujita Seed Company P.O. Box 211 Osaka C.

Sakata & Co. 2 Kiri batake, Kanagawa-Ku Yokohama, Japan

Takii & Co. Ltd. Seed Growers P.O. Box 7 Kyoto Central Kyoto

.

Kenya

Kirchhoff’s East Africa P.O. Box 30472 Nairobi

The Netherlands

Nunhem’s Zaden Hael en

Royal Sluis P.O. Box 22 Enkhuizen

Sluis & Groot Westeinde 62 Enkhuizen

. .

Philippines

Bureau of Plant Industry Economic, Garden Los Baiios Laguna

Farmers Seed Co. 415 Aldedoa St. P.O. Box 4158 Manila

Taiwan

Taiwan Seed Service Shinshieh Taichung, Taipei

Known-you Nursery 26 Chung-Cheng 2nd Road Kaohsiung

United Kingdom

United Kingdom

Sutton bc Sons Ltd. Seed Growers k?ding

U.S.A.

Asgrow Seed Company P.O. Box 72 Milford Connecticut

Burpee Co. Seed znd Bulb Growers Phib felphia 47 Pennsylvania

Dessert Seed Co. P.O. Box 187 El Centro California

Ferry-AMorse Seed Co. P.O. Box 188 Mountain View California

Harris Seed Co. Rochester, New York 14624

Petoseed Co. P.O. Box 4206 Satocoy California 93003

Denmark

J.E. Ohlsen Enke Ny Munkegaard Taastrup Copenhagen

I

. .

Hurst Gunson Cooper Taber Witham Essex

34

6. LITERATURE

The most relevant publications consulted by the author are presented in the following annotated list. For more detailed information on certain subjects of vegetable seed production and technolo,T it is recommended to consult the following ab- strict journals: 1 Horticultural Abstracts. Published by the Commonwealth Bureau of Horticulture

and Plantation Crops, East Mailing Research Station, Maidstone, England; 2. Plant Breeding Abstracts. Published by the Commonwealth Agricultural Bureaux,

Famham Royal, Slough, England: 3. Abstracts on Tropical Agriculture. Published by the Department of Agricultural

Research, Royal Tropical Institute, Amsterdam, The Netherlands.

When requiring information on vegetable growing in a given area, contact first of all the local Agricultural Extension Services. They often provide extension bulletins and information on where to obtain useful handbooks on vegetable growing, writ- ten especially for the given country. These local or national vegetable handbooks are not presented in the following list. It only mentions those handbooks which have a broader significance. iMuch information on vegetable growing and seed production can be found in libraries of hgricultural Universities and Horticultural Research Institutes.

Anonymus 1961. &&zul#ural and horticultural seeds. FAO Agricultural Studies no. 55, Rome; 531 p. (a guide for professional seed producers)’

- 1961. Seeds The Yearbook of Agriculture 1961. The United States Department of Agriculture. (information on seed production and processing in the USA)

- 1969. Equipment numbers. Proc. Int. Seed Test. Ass. Vol. 31 no. 1: 177 p. (description of equipment and techniques for cleaning, sampling and testing seeds)

- 1976. International Rules for Seed Testing. Rules 1976. Int. Seed Test. Ass., Seed Sci. & Technol. 4 (1): l-180 (international rules for seed testing with detailed instructions; French edition: 4(4): 558-751)

- 1978. Symposium on seed problems in horticulture. The search for practical solutions. Acta Horticulturae 83: 321 p. (a survey of ongoing research and developments in seed production and technology of vegetables; the paper of R.A.T. George, p. 23-29, deals with problems of seed production in developing countries)

Chauhan, D.V.S., 1972. Vegetable production in India. Ram Prasad & Sons, Agra-3; 325 p. (handbook for extension workers in India and surrounding countries)

Chondhury, B. 1976. Vegetables. India, the land and the people, New Delhi; 227 p. (handbook for extension workers in India and surrounding countries)

35

Chupp, Ch. and A.F. Sherf, 1960. Vegetable Diseases and Their Control The Ro- nald Press Company, New York; 693 p. (handbook for vegetable diseases, including many tropical vegetable types)

Epenhuijsen, C.W. van, 1974. Growing native vegetables in Nigeria. FAO, Rome; 113 p.

,:, ._

-

(description of small-scale seed production; cultivation of local vegetables useful for the hot-humid tropical area of West and Central Africa)

Filgueira, F.A.R., 1972. Manual de olericultura. Cultura e comercializacso das hor- tilicas. Sao Paula; 460 p. (handbook for vegetable growing in Portuguese, for Brazil; typical tropical vegetable types are poorly described)

Fundacion Shell, 1968. Hortalizas. Cagua, Venezuela (FUSAGRI); 136 p. (guide for commercial vegetable growing in Venezuela, in Spanish; useful to other Spanish speaking countries with subtropical conditions)

Grubben, G.J.H., 1977. Tropical vegetables and their genetic resources. Edited by H.D. TINDALL and J.T. WILLLCMS, International Board for Plant Genetic Re- sources, FAO, Rome: 197 p. (data on economic and nutritional importance, agronomy, seed production, recommendations for germplasm collection, breeding and research)

Hadfieid, F., 1960. Vegetable gardening in Central Africa. Pumell and Sons, South Africa (Pty) Ltd.: 178 p. (handbook for Central .4frica, more suitable for mountainous areas than ‘for lowland)

Harrington, J.F., 1972. Seed storage and longevity. In: KOZLOWSKX T.T. (ed.), Seed Biology, Academic Press, New York and London, Vol. III: 145244 (a comprehensive description of theoretical background and practical implica- tions of seed storage)

Hawthorn, L.R. and L.H. Pollard, 1954. Vegetable and fzower seed production. Blakiston, New York, 626 p. (the most popular handbook for vegetable seed production, also outside the USA;

Herklots, G.A.C., 1972. Vegetables i;t South-East Asia George Allen Xc Unwin, London; 525 p. (handbook for vegetable growers in S.E. Asia and elsewhere in the low hmmid tropics;‘the typical tropical vegetable types are well described)

Hill, A.G.G., 1948. Seed production of European vegetables in the tropics. Com- monwealth Bureau of Horticultural and Plantation Crops, Technical Communica- tion 19: 28 p. (a review of experience in this field until 1948)

Knott, J.E., 1966. Handbook for vegetables growers. Wiley and Sons, Inc., New York, London, Sydney; 245 p. (handbook with tabulations giving detailed information on vegetable growing techniques and seed production in temperate or subtropical areas)

Knott, J.E. and J. Deanon, 1967. Vegetable production in South-East Asia. Univ. Philippines, Manila; 366 p. (handbook for research workers in S.E. Asia, also useful for other humid tropical

,

areas) Messiaen, C.M., 1975. Le potager tropical. Tome 1, Giniralitis. Tome 2, Cultures

sptciales. Tjme 3, Cultures spiciales. Presses Universitaires de France. Paris;

36 I

470 p. (handbook for practical vegetable growing, in French, especially for the Carib- bean area, also suitable for other tropical lowland areas; extensive description of vegetable diseases)

Ochse, J.J. and R.C. Bakhuizen van den Brink, 1931. Vegetables of the Dutch East Indies. Bogor. Reprint Elsevier, Amsterdam, 1977; 1004 p. (classical work on tropical vegetable s, for botanically interested research workers)

Oomen, H.A.P.C. and G.J.H. Grubben, 1976. Tropical Leaf Vegetables in Human Nutrition. Comm. 69. Department of Agricultural Research, Royal Tropical In- stitute, ,:z+~srerdam; 136 p. (guide for home gardening and for the cultivation of tropical leaf vegetables)

Roberts, E.H. (ed.), 1972. Viability of seeds. Chapman and Hall, London: 448 p. (basic principles of seed viability, for research workers and seed technologists)

Ruck, H.C., 1976. Horticulture, a select bibliography. F.40 Plant Production and Protection Papers 1. Food and Agriculture Organization of the United Nations, Rome; 56 p. (a list of publications on horticulture in developing- countries, including vegetables, fruits and ornamentals)

Terra, G.J.A., 1966. Tropical Vegetables. Comm. 54, Department of Agricultural Research, Royal Tropical Institute, .4msterdam; 107 p. (botanical iist of tropical vegetables, giving much information on cultivation, for research workers interested in taxonomy and human nutrition)

Tooie, E.H., V.K. Toole and E.A. Gorman, 1948. Vegetable seed storage as affected 3y temperature and relative humidity. USDA Techn. Bull. 972: 24 p. (description of an experiment with seed of 15 common vegetable types)

Tindall, H.D., 1968. Commercial vegetable growing. Oxford Tropical Handbooks. London; 300 p. (concise handbook for vegetable growing in the tropics, including many tropical type vegetables)

Winters, HF. and G.W. Mikimen, 1967. Vegetable gardening in the Caribbean area. Agricultural Handbook, 323,USDA Agric. Research Service; 114 p. (handbook for vegetable growing in the Caribbean area)

37 ”

7. NAMES OF VEGETABLES COMMONLY CULTIVATED IN THE TROPICS’

Lntin

1. Solanaceae Capsicum annuum Capsicum spp. Lycopersicon es-

culentum Solanum macroc0-

Pan Solanum melongena

2. Cucurbitaccae Benincasa hispida Citrullus vulgan~ Cucumis melo Cucumis sativus

Cucurbita moschata Cucurbita pepo Lagenaria lcucan-

tha Luffa SW. Momordica charan-

tia

Rkhosanthes q+za

3. Legnminosac Cajanus cajan Canavalia ensifor-

mis Dolichos lnblab Glycine max. Pachywhyzus

ermus Phas -01~s lunutus

PEAeolus radiutus

Phase&s vulgaris

Pisum sativum

English

Solanaceac sweet pepper hot pepper tomato

African eggplant

eggplant, brinjal

C&mbits wax gourd watermelon melon cucumber, gherkin pumpkin squash bottle gourd

loofah bitter gourd bitter melon, bitter cucumber snake gourd

Legumes pigeon pea sword bean

hyacinth bean soy bean yam b&n

Lima bean

mung bean

common bean

pea

French

SoIanCes poivron piment tomate

aubergine locale

aubergine

Cucurbitacecs courge cireuse pastkque melon concombre

courge courgette calebasse

loofah margose, concombre

amer

serpent vCg&.l

LCgurnineuses pois d’Angole pois sabre

dolique d’Egypte soya dolique bulbeux

haricot Kissi

haricot velu haricot & gram

vert haricot vert

petit pois

I

-.

Spanish

Solaniceas pimrnt;>n Chile, aji tomate

berenjena

Cucurbitaceas calabaza china sandia m&n pepino

calabaza calabaza calabaza

patola cundeamor, am-

palaya

patola .

LCgUIllillOsaS

guisante de paioma haba blanca

lablab, batao soya jicama de agua

frijo! trepador, judia de Lima

frijol mung0

habichuela, ejote, frijol comun, vainitas arveja, guisante

1. only vegetable species propagated by dry seed.

Latin

Psophocarpus tetra- gonolobus

Vicio faba V&ma unguiculata

Voandzeia sub terra- flea

4. Cruciferae Brassica campes-

tris var. chinensis Brassica campes-

tn’s var. pekinen- sis

Brassica campestris var. rap4

Brassica carinafa Brassica juncea

Brassica oleracea var. acephda

Brassica oleracea var. bo try tis

Brassica oleracea var. botrytis

Brassica oleracea var. capitata

Raphanus sattius

5. (various species)

Amaranthus spp.

Basella alba

Corchoncs olito- TiUS

Ipomoea aquatica

Solonurn n&urn

Talinum trikngulare

Tetragonia expansa

English

wing bean, Goa bean

broad bean yardlong bean, asparagus bean

Bambara groundnut

Crucifers Chinese cabbage

(pakchoi) Chinese cabbage

(petsai)

turnip

African cabbage mustard

kale, borecole

cauliflower

broccoli

(white) cabbage

radish

tropical leaf vegetables

amaranth

Basella, Ceylon spinach

jute, jews mal!ow

kangkong, water spinach

nightshade

Talinum, water leaf

New Zealand spinach

French

pois carrC

f&c

dolique-asperge, nikbbi

voandzou

Crucifires thou de Chine

thou de Chine

navet

thou africain moutarde de

Chine thou vert

choufleur

broccoli

thou

lid.5

Ibgumes-feuilles tropicaux

arnarante

baselle

jute

patate aquatique

morelle noire

gEl3SC

tttragone

Spanish

sesquidillas

haba

chaucha por metro, frijol de ojo negro, nitao

Cruc iferas co1 China

co1 China

nabo, rutabaga

mostaza

co1 berza

coliflor

broccoli

rep0110

hojas vegetales tropicales

amaranto, bledo, tampala

espinaca de Ceilti

we

espinaca acquitica

yerba mora, morella

espinaca de Filipinas

espinaca de Nueva Zelandia

Latin EngliFh Spanish

algunas especies para temporadas dlidas

quingbmbo

French

6. (various species) various hot- season specie3

diffirentes espikes des saisons chaudes

gombo Hibiscus esculen- tUS

Hibiscus sabdan’ffa

okra

roselle oseille de Guinie

mai’s

a’grio de Guinea

Zea mays sweet corn maiz dulce, elote

7. (various species) various cool- season species

diffkrentes espkces des &sons fraiches

oignon ciboule

algunas especies para temporadas frias

ceboila cebolleta

Allium cepa Allium fistulosum

onion Japanese bun-

ching onion leek celery asparagus

Allium porrum Apium graveolens Asparagus offici-

nalis Beta vulgaris var.

cicla Beta vulgaris var.

ntbra Cichonwk endi-

Via Daucus care ta Lactuca sativa Spinacia oleracea

poireau celeri asperge

puerro apio .esp;trago

spinach beet poiree acelga

garden beet betterave remolacha

endive Chico&e escarola, en- divia

zanahoria lechuga espinaca

carrot lettuce spinach

carotte laitue Cpinard

40

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